Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 170225

Area Forecast Discussion
National Weather Service Huntsville AL
925 PM CDT Sun Jun 16 2019

.NEAR TERM...(Rest of tonight)
Issued at 925 PM CDT Sun Jun 16 2019

Afternoon convection has waned this evening with the loss of heating
and a partly cloudy sky and very humid conditions remain in their
wake. 02z temperatures remain quite mild, thanks to the increasing
cloud cover and dewpoints around 70 degrees. For this reason, would
expect lows stay in the lower 70s most valley areas tonight, much
warmer that what was observed a few nights ago. As eluded to above,
cloud cover will continue to increase overnight due to blow off
cirrus from deep convection to the west. A current glance at
satellite and radar trends suggest most of the shower/thunderstorm
activity will remain displaced to the south and west of the area.
However, with some lingering outflow boundaries in place in this very
moist environment, an isolated shower or storm cannot be ruled out
for the remainder of the overnight hours. However, with no upper-
level support, expect a mainly dry night across the region.

.SHORT TERM...(Monday through Monday night)
Issued at 258 PM CDT Sun Jun 16 2019

The synoptic pattern begins to grow more favorable for organized
storm development as we get into the work week. Southwesterly flow
will deepen throughout the day Monday, keeping showers and
thunderstorms possible due to another day of humid, unstable air.
With high temperatures in the upper 80s and and dew points in the
lower 70s, it will certainly make for a muggy start to the week.

Confidence begins to increase later tomorrow evening and overnight
as a shortwave trough moves east from the Southern Plains and
approaches the TN Valley region. This will provide enough forcing for
organized thunderstorm development tomorrow night. Although
widespread severe thunderstorms are not expected at this time, these
storms could pose a damaging wind threat through the overnight hours.
Overnight lows will be near 70 degrees as southerly flow and cloudy
conditions persist.

.LONG TERM...(Tuesday through Sunday)
Issued at 258 PM CDT Sun Jun 16 2019

The extended portion of the forecast begins Tuesday morning, with
ongoing showers and storms likely to start the day. The trend will
only increase in coverage through the afternoon hours as a shortwave
moves across Nrn AL/Srn Middle TN during this time. As has been the
case for much of the forecast period as a whole lately, gusty winds
and locally heavy rainfall will be the primary threats. This is
mainly thanks to MLCAPE values approaching 3000 J/kg and increasing
PWat values upwards of 1.9-2". This will also enhance precipitation
loading in any convection, which will aid in downdrafts producing
winds in the range of 30-50mph at times (or higher within the
stronger cells).

The difficult part of the extended forecast revolves around the exact
timing of these rounds of storms. On Monday/Tuesday, a shortwave
moves across the region, which is rather easy to time. Beyond that, a
weak frontal boundary arrives and washes out by Wednesday, with this
providing a guide for convection to form/meander across through
Friday. Disturbances aloft will wobble across the area from W to E,
bringing several rounds of showers and storms to the TN Valley
through the end of the week. GFS/ECMWF hint at the most widespread
convective activity during this time occurring overnight Wednesday
into Thursday, with likely/definite coverage during this time.
Coverage will wane as we head into the weekend, though we`ll still
see (at least) isolated to scattered coverage W to E during this
time. Rainfall totals over the next 5-7 days look to be in the
1.5-2.5" range, with isolated higher amounts in excess of 3"

It`s at this point in the GFS/ECMWF where model agreement diverges
with respect to upper level features. Whereas the GFS advertises weak
ridging aloft in the Plains, this would spell a march of MCSs for us
as disturbances develop and ride up/over the ridge to our W. The
ECMWF, however, has a large-scale trof in place over the
Intermountain W and much of the Central Plains, with upper level
ridging in place over us, which would spell a drier (and warmer)
pattern for the local area.

Either way, it`s going to be an active pattern for much of next week,
eventually waning somewhat for the weekend. Temperatures for the week
ahead will be rather seasonable, topping out in the lower/middle 80s
on rainier days, and middle/upper 80s (with even some lower 90s
possible) on the drier days. Morning lows will remain rather similar
each day, starting out around 70F.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 642 PM CDT Sun Jun 16 2019

Afternoon convection will quickly wane with the loss of heating,
resulting a quiet and dry overnight period. BKN/OVC decks of mid to
high clouds will filter across the area ahead of an approaching
storm system from the west. Ceilings will lower to low-end MVFR
Monday morning, and have added a mention of VCTS in the afternoon at
both sites to account for scattered diurnal convection that will
develop. Was not confident to go prevailing yet, but this may need to
be added in a future TAF issuance.





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