SPC Jan 15, 2021 2000 UTC Day 1 Convective Outlook

SPC Jan 15, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0139 PM CST Fri Jan 15 2021

Valid 152000Z - 161200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few brief thunderstorms are possible over the middle Ohio Valley
to Cumberland Plateau this afternoon.

...20z Update...

The ongoing forecast remains on track and no changes have been made
with this update.

..Leitman.. 01/15/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Fri Jan 15 2021/

...Lower/Middle Ohio Valley to Cumberland Plateau...
Cold mid-level temperatures (low to mid -30s C at 500mb) associated
with the Midwest-centered cyclone will overspread the region through
tonight. Relatively cloud-free skies over the Lower/Middle Ohio
Valley and Cumberland Plateau will contribute to a further
steepening of low/mid-level lapse rates this afternoon. Even while
mixing/low-level drying will tend to occur, a warming boundary layer
with scant moisture/buoyancy may be sufficient for a few low-topped
thunderstorms this afternoon.

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SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook Image
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1249 PM CST Fri Jan 15 2021

Valid 161200Z - 171200Z

...CRITICAL FIRE WEATHER AREA FOR PARTS OF SOUTHERN CALIFORNIA...

The Critical delineation across southern California has been
expanded eastward to include the San Bernardino Mountains, as the
latest high-resolution model guidance depicts 15% RH and sustained
offshore winds exceeding 25 mph during the afternoon. Critical
winds/RH are otherwise still expected westward across the San
Gabriel Mountains into the Ventura Valley area. Latest guidance
consensus also shows widespread high-end Elevated conditions
southward along the San Jacinto to Laguna Mountain ranges. While at
least locally Critical conditions may occur, there is enough
disagreement among the high-resolution guidance to forego further
Critical expansions at this time. 

Locally Elevated/Critical conditions are also possible across far
southern New Mexico into the Trans Pecos region of Texas. However,
fuels across the region remain marginally supportive of significant
wildfire spread potential. Given the marginal receptiveness of fuels
and the localized nature of the more favorable surface wind/RH
overlap, no fire weather highlights have been added to southern New
Mexico/southwest Texas at this time.

Lastly, RH may drop into the 30-35% range across portions of
southern Georgia into the Florida Panhandle tomorrow. While winds
may increase to 15 mph by afternoon peak heating in some locations,
the overall lack of more receptive fuels precludes any fire weather
highlights at this time.

..Squitieri.. 01/15/2021

.PREV DISCUSSION... /ISSUED 0156 AM CST Fri Jan 15 2021/

...Synopsis...
Upper-level ridging over the West Coast will maintain dry weather
for southern California as well as re-intensify an inland surface
high over the inter-mountain West. A strengthening offshore pressure
gradient across southern California will support another day of fire
weather concerns. Elsewhere, a weakening pressure-gradient across
the Plains and into the eastern CONUS will limit the coverage of
breezy conditions, though a few locations may see some fire weather
concerns where terrain-augmented winds and sufficiently reduced RH
can overlap. 

...Southern California...
Surface high pressure is expected to re-intensify over the northern
Great Basin from late Friday night into Saturday due to upper-level
height rises over the West Coast. This will support a -5 to -7 mb
LAX-DAG pressure gradient beginning early Saturday morning through
the afternoon. Although breezy conditions appear likely (sustained
winds at 20-30 mph with gusts to 40 mph), mid to upper-level support
does not appear to be as favorable as Friday and will limit the wind
potential. However, poor RH recoveries (10-20%) through Saturday
afternoon will support elevated to critical fire weather conditions.
Confidence in sustained critical conditions is mainly limited to
portions of Los Angeles and Ventura counties where low to mid-level
winds are forecast to be the strongest, though transient critical
conditions may extend as far south as the U.S./Mexico border. There
are some indications that the offshore pressure gradient may persist
into Sunday, which could support additional fire weather concerns
for very early Sunday morning at the end of the Day 2 period.
However, confidence in this potential is somewhat low.

...Southern High Plains...
Westerly downslope winds are forecast to increase through Saturday
afternoon within the higher terrain of eastern New Mexico and
southwest Texas. RH values in the 15-20% range will support some
areas of elevated, to perhaps critical, wind/RH conditions. However,
marginal fuels across this region and the spatially limited nature
of the threat preclude the need for highlights.

...Please see www.spc.noaa.gov/fire for graphic product...

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SPC Jan 15, 2021 1730 UTC Day 2 Convective Outlook

SPC Jan 15, 2021 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1102 AM CST Fri Jan 15 2021

Valid 161200Z - 171200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Saturday.

...Synopsis...

A synoptic upper low over the OH/TN Valleys Saturday morning will
pivot northeast through the period, becoming oriented over ME and
offshore from the New England coast Sunday morning. A shortwave
upper trough diving southeast across the Plains to the mid-MS Valley
will reinforce the arctic airmass over much of the central/eastern
U.S. As a result, seasonally cold and dry conditions are expected,
limiting instability and precluding thunderstorm development.

..Leitman.. 01/15/2021

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SPC Jan 15, 2021 2000 UTC Day 1 Convective Outlook

SPC Jan 15, 2021 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1025 AM CST Fri Jan 15 2021

Valid 151630Z - 161200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few brief thunderstorms are possible over the middle Ohio Valley
to Cumberland Plateau this afternoon.

...Lower/Middle Ohio Valley to Cumberland Plateau...
Cold mid-level temperatures (low to mid -30s C at 500mb) associated
with the Midwest-centered cyclone will overspread the region through
tonight. Relatively cloud-free skies over the Lower/Middle Ohio
Valley and Cumberland Plateau will contribute to a further
steepening of low/mid-level lapse rates this afternoon. Even while
mixing/low-level drying will tend to occur, a warming boundary layer
with scant moisture/buoyancy may be sufficient for a few low-topped
thunderstorms this afternoon.

..Guyer.. 01/15/2021

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SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook Image
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1007 AM CST Fri Jan 15 2021

Valid 151700Z - 161200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

Critical conditions are ongoing across portions of the southern
Transverse Ranges in southern California. The LAX-DAG pressure
gradient has been sustained around -7 mb over the past few hours,
with multiple ASOS sites showing RH dipping below 20% to under 10%
in some spots, and offshore winds sustaining in the 15-20 mph range.
Latest model guidance consensus, including the latest
high-resolution guidance, suggest that the very low RH is expected
to prevail through the forecast period (12Z Saturday morning).
Critical conditions should prevail through early afternoon, with the
pressure gradient and associated surface wind field expected to
relax somewhat by mid to late afternoon, though higher-end Elevated
wind/RH should persist. As such, no changes have been made to the
current California fire weather highlights.

No changes were also made to the Southern Plains highlights, as
high-end Elevated conditions are also expected during the afternoon,
when temperatures warm into the 50s F. Current METAR observations
across the southeast Colorado/southwest Kansas/OK and northern TX
Panhandle areas show sustained 30-40 mph northwesterly winds with RH
dropping well below 30%, but with temperatures predominantly below
40 F. Additional diurnal heating will allow RH to drop into the
10-20% range by mid to late afternoon, with northwesterly winds
remaining above 25 mph across much of the southern High Plains, as
depicted by the latest model guidance consensus. While the forecast
surface wind/RH would typically necessitate Critical highlights,
fuels remain modestly receptive to fire spread, so Critical
delineations have been withheld.

..Squitieri.. 01/15/2021

.PREV DISCUSSION... /ISSUED 0118 AM CST Fri Jan 15 2021/

...Synopsis...
A strong upper-level low will continue to deepen across the eastern
two-thirds of the CONUS today. An attendant surface low in place
across the Midwest will begin to gradually weaken through the day.
However, this low juxtaposed next to a strong surface high over the
inter-mountain West will maintain strong pressure gradient winds
over much of the Plains. Additionally, this surface high will
continue to promote offshore flow over southern California and
maintain fire weather concerns. 

...Southern California...
Early morning surface observations show elevated to critical fire
weather conditions already ongoing across portions of Los Angeles,
Ventura, Orange, and southwest San Bernardino counties. RH values in
the low teens are noted with wind gusts up to 30-45 mph in some
locations. These conditions are being driven by a building 1040 mb
surface high to the north across the northern Great Basin. Guidance
continues to suggest a -5 to -8 mb LAX-DAG pressure gradient will
foster strong winds with gusts between 40-60 mph (possibly up to 70
mph for some locations) across coastal southern CA through at least
mid-day before gradually abating late this afternoon. Poor RH
recoveries (generally in the upper single-digits to teens) are
expected through this afternoon and will help support the fire
weather threat.

...Central to Southern Plains...
Pressure gradient winds are expected to increase through the day
with sustained winds near 25-35 mph and gusts up to 45-60 mph.
Mostly clear skies along with modest dry air advection from the
north will help RH values fall into the 15-30% range by this
afternoon. The elevated risk area has been expanded to include
portions of eastern CO and western KS where winds are forecast to be
the strongest. Although temperatures are forecast to remain cool for
eastern CO/western KS, recent reports from the ND/SD border of a
fast-moving grass fire under similar weather conditions suggest that
rapidly growing fires can develop given sufficiently dry fine fuels.
While critical wind/RH thresholds may be met today, the fire weather
threat will be conditional due to somewhat higher fuel
moisture/lower ERC values compared to locations further north. Areas
that see rapid drying of fine fuels through the day may see a
heightened fire weather threat, but given the uncertainty of fuel
conditions no critical areas are introduced.

...Please see www.spc.noaa.gov/fire for graphic product...

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