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


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


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/

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


Thunderstorms are not expected on Saturday.


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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